Automatic pneumatic impact hammer



Sept. 2, 1969 a. T. WARD 3,464,501

AUTOMATIC PNEUMATIC IMPACT HAMMER Filed Oct. 5, 1967 2 Sheets-Sheet l 7m m w J. 7 W M j mz a M F M a 2 w 2 a 0 W 3 I I I Ml l lfl l l ll rilmrll IIIIJ I I I l I 1| W W 2 Shets-Sheet 2 5 R? z W a m p WW m u,(mid v 5 H: J fi w wwwf 2 P MN m 4 l, 4 M

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Sept. 2, 1969 E- T. WARD AUTOMATIC PNEUMATIC IMPACT HAMMER Filed Oct.1967 United States Patent 3 464 501 AUTOMATIC PNEUMATIC IMPACT HAMMEREugene T. Ward, Highland Heights, Ohio, assignor to Allied Steel &Tractor Products, Inc., a corporation of Ohio Filed Oct. 5, 1967, Ser.No. 673,121 rm. c1. B23q 5/06; 1321c 5/08 US. Cl. 173-17 2 ClaimsABSTRACT OF THE DISCLOSURE This invention relates to improvements inpneumatic hammers and, more particularly, to large pneumatic hammersmounted on and manipulated by construction machinery, such as a tractorequipped with a backhoe boom, and the like.

In construction work, demolition work for new construction, mines,quarries, mills, in fact nearly everywhere that the well-knownair-driven jack hammers are and have been employed, there has been along standing need for impact hammers which are more massive than thosewhich can be handled by one or two men and yet which are more flexibleand manipulatable than rather difficultly mobile power hammers, such asmobile pile drivers and the like. Such large manipulatable impacthammers have been proposed for mounting on the booms or dip-sticks oftractor-mounted backhoes, grading machinery, frontend loaders, or thelike, by which the hammers tool bit can be manipulated between verticalto horizontal planes or otherwise positioned for the optimum effect ofits impact. With such machine-manipulated hammers, weighing in the orderof 1,000 pounds, the tool can be driven, with compressors of standardsizes for manual jack hammer crews, so as to deliver energy at the rateof 300,000 foot/pounds per minute. In many demolition jobs, as indemolishing reinforced concrete pavements, foundations, etc., suchhammers, especially if made according to this invention, willout-perform crews operating to 25 conventional jack hammers. One reasonfor the high performance of such large impact hammers is not so much therate of delivering energy as it is the amount of energy delivered in asingle blow at a fairly high rate of speed, i.e., in the order of 1,000foot/pounds per blow (at the rate of 300 per minute).

The very massiveness of such machine-mounted high impact hammers and theconsequent difliculty of controlling them heretofore militated again-sttheir general use and caused frequent and expensive breakdowns whenused. Heretofore, an operator of a construction machine for manipulatingsuch a massive impact hammer has his hands full in either operating thehammer or in operating the machine to position the hammer. Heretoforethe most successful of such massive impact hammers were operated byvalves which were manually opened by the operice ator after the hammerhad been positioned and closed when the tool had broken through or toallow the operator to reposition the hammer. Not only was the efficiencyreduced because the operator had to perform his duties of positioningthe hammer and operating it in succession, but many breakdowns, oftenattributed to other causes, were due to the fact that the operator hadno feel of the load on the hammer bit, and the hammer would operate whenthere was no resistance load on the bit, even though the hammer mighttheoretically be ported, according to previous constructions, to stopwhen the hammer bit encountered no resistance.

It is an object and advantage of this invention to provide an impacthammer which is automatically operated by the positioning of the hammerby the operator and which automatically ceases operation when the hammertool no longer encounters resistance, either due to the fact that theoperator has removed the hammer from the load or the tool has brokenthrough or otherwise completed its work at the moment. More efficientoperation is thereby attained and breakdowns are minimized.

Other objects and advantages of this invention will be apparent from thefollowing claims and the detailed description, and drawings of oneembodiment in which:

FIGURE 1 is a small diagrammatic elevation showing an impact hammer madeaccording to this invention mounted for manipulation on the boom of abackhoe equipped tractor.

FIG. 2 is an enlarged side elevation of the hammer shown in FIG. 1.

FIG. 3 is an end view, taken from the line 33 of FIG. 2.

FIG. 4 is a detailed front elevation of the hammer shown in FIG. 2,partly broken away to show the positioning of the significant elementswhen the hammer is in operation.

FIG. 5 is a view similar to FIG. 4, but showing one positioning of thesignificant elements when the hammer is operative.

FIG. 6 is an enlarged detail of the mating shoulders of the tool shankband and the tool retainer, taken from FIG. 4.

FIG. 1 shows a hammer 10 made according to this invention mounted on theboom 2 of a vehicle 3 representing, diagrammatically, a tractor equippedwith a back-hoe mechanism in which the back-filling bucket has beenreplaced by the hammer 10. As indicated above, the particular type ofvehicle upon which hammers made according to this invention may bemounted is purely a matter of choice determined by the availablevehicles and the jobs to be done. In practice such vehicles have variedfrom universal road-grading machines having a boom arrangementpermitting substantially fully universal angular movement of theattachment on the end of the boom to simple fork-lift trucks With thehammers mounted in place of the lifting forks. The cylinder of thehammer 10 is connected by the air-line 4 to an adequate source ofoperating compressed air, not shown, but usually a portable motor-drivencompressor unit as commonly used on construction jobs.

As evident from FIGS. 2 to 5, the main structural elements of the hammer10 comprise, in the embodiment shown, an elongated cylinder block 11 andend members comprising a cylinder intake head 12 and a tool retainerhead 13, all, except as the intermediate portion of the cylinder blockis relieved at its corners, essentially rectangular in horizontalcross-section. These members are held in longitudinal alignment by fourtie-bolts 14 extending through openings drilled longitudinally throughthe corners. While not directly relevant to the principal feature ofthis invention, it should be pointed out that the tie-bolts 14 and theopenings in which they are re ceived are preferably carefully machinedto provide a close sliding fit between the bolts and the alignedopenings; this, together with the setting of equal tension on thetie-bolts by means of the pinned end nuts and cap nuts 16, aids inmaintaining, during operation, alignment between the cylinder block 11and its end members 12 and 13. This alignment is also obtained by theboss and recess fit as shown between the block 11 and retainer 13 inFIGS. 4 and 5. The tie-bolts 14 are preferably of high-tensile steel,machined and polished to remove all nicks between the enlarged threadedportions which might initiate a fracture; these bolts should not onlybear, without deformation beyond their elastic limit, the fulllongitudinal force of the hammer whenever the tool suddenly breaksthrough substantial resistance but also the wedging or side loads whichthe tool encounters during operation of the hammer.

The entire hammer 10 is carried by the support plates 17 having drilledholes 18 for bolting to a boom 2. The plates 17 carry pads 19 whichclosely fit in the ways 20 cut in the cylinder block 11. The block 11 isthus removably locked between the plates 17 by means of the clampingstuds 21 and the dowel studs 22, the latter extending through the plates17 and pads: 19 into the block 11.

As indicated in FIGS. 4 and 5, the cylinder block 11 is provided with acentral longitudinal bore 25, counterbored at its lower end to receive atool bushing 26. Parallel to the bore 25 in the wall of the block 11 isone or more return passageways 27 connecting the valved intake head 12to a lower return port 28 opening into the bore 25. The bore 25 isported to the atmosphere in its upper portion by an impact exhaust port29 and near its lower end by one or more return-disactivating ports 30drilled through the bushing 26 and through so much of the pad 19 andplate 17 that, as shown in FIGS. 4 and 5, the positioning of theselatter members otherwise might block and thereby effectively alter theposition and capacity of the ports 30.

As indicated in FIGS. 4 and 5, the bore 25 receives a heavy ramreciprocal in the bore as a free piston. The upper end of the bore 25 isclosed by the intake head 12 having an intake port 31 to which an airpressure hose 4 may be connected; the intake head is also provided withsuitable valving exhaust ports opening, in this instance, into thecircumferential gap 32 between the head 12 and block 11. Within the head12 is an automatic valve V which admits air under pressure when thefree-piston ram 35 is in the upper end of the bore 25 until the ram isdriven forward in an impact stroke so as to clear the exhaust port 29.In response to the pressure drop in the upper end of the bore, the valvecloses the upper portion of the bore 25 to line pressure and opens it toexhaust through the gap 32 while admitting line pressure to thepassageway 27 and port 28; thus, if the tool is under load, as explainedbelow, the ram 35 will be returned to the upper portion of the bore 25to position the ram for an impact stroke and repetition of theram-reciprocating cycle. Automatic valves such as the valve V, usuallyof a poppet and sleeve type, are conventional in the pneumatic hammerart and since at least several of such valves are available andoperable, the valve V is indicated only diagrammatically.

The lower end of the cylinder bore 25 is closed by a tool carried by thetool retainer head 13. A tool 40 comprises a shank having an upperportion 41 and a lower portion 42 on either side of an integral enlargedshank band 43. The body of the tool below the shank terminates in an endshaped according to the specific job for which the hammer is to beemployed. The pointed end shown is for general demolition work; chiselends are generally employed for line breaking of pavements and flat endsfor compacting or post driving; also, the end may be equipped with asuitably shaped fitting for driving sheet piling and the like. Tools 40,provided with the above-described shank construction, are readilyinterchangeable in the hammer, either to accommodate it for differentjobs or for replacement of worn or broken tools; this is accomplished bysimply disconnecting the retainer head 13 from the cylinder block 11,replacing a tool, and then reconnecting the retainer head.

As indicated in FIGS. 4, S and 6, the retainer head 13 is provided witha central bore 45, axially aligned with the cylinder bore 25, and also acounter-bore 46 to receive the shank band 43. It is to be noted, asshown in detail in FIG. 6, that the shank band 43 merges into the lowershank portion 42 by convex and cancave fillets to provide a filletedshoulder 47 which, when the tool 40 is in its lowermost position in theretainer head 13, mates with an oppositely filleted shoulder 48 at thejuncture of the counter-bore 46 with the bore 45 on the barrel 49 of theretainer head 13.

Referring to FIGS. 4 and 5, it is to be noted that the axial length ofthe shank band 43, and the length of the upper shank portion 41 areproportioned, with respect to the depth of the counter-bore 46, so that,when the shoulder 47 of the tool 40 is engaged with the shoulder 48 ofthe retainer head, an appreciable length of the shank portion 41 isengaged and guided in the closely fitting bushing 26. Likewise, the head36 of the ram 35 is tapered so as to engage the top of the tool 40 whenthe tool is in the lowermost position in the retainer 13 while providinga slight clearance with the bushing 26. The length of the upper shankportion 41 is somewhat greater than or at least substantially equal tothe length of the bushing so that when the shank band 43 engages thelower end of the bushing 26 as a stop, the upper shank portion 41extends above and thereby closes the return-disactivating ports 30. Thereturn port 28 is located in the bore 25 so that it is closed by thecylindrical body of the ram 35 when the tool is in its lowermostposition in the retainer 13, as shown in FIG. 4. The port 28, however,is opened to the space between the tapered head 36 of the ram when thetool is in its uppermost position and, the ram reciprocates between thesolid line and dot-and-dash line positions, as shown in FIG. 5, in theoperating cycle of the impact hammer.

The automatic control of the hammer operation by its above-describedports is as follows: With the point of the tool 40 out of contact withthe surface to be struck, as it will be when the tool is being moved toits desired position by the operator, the tool 40 and ram 35 will be inthe disactivated position shown in FIG. 4. This will be due to gravityand/or the ram-disactivating effects of the ports 30 and the filletedshoulders 47 of the shank band 43 and the mating shoulder 48 of thebarrel 49 of the tool retaining head 13. In this disactivated position,the air-line operating pressure is switched by the valve V to thepassageway 27, but its port 28 is not only closed by the body of the ram35, but the ports 30 vent to the atmosphere the leakage from the ports28, which leakage occurs due to the necessary tolerance and unavoidablewear between the ram 35 and the bore 25 and, in the absence of the ports30, could otherwise build up to an activating pressure around the ramhead 36. As the operator positions the hammer so that the tool pointengages the surface to be hammered and moves the hammer toward suchsurface, the tool is automatically forced to the position shown in FIG.5, where the tool shank closes the ports 30 and the ram head 36 is movedback to uncover the port 28 and commence the operating cycle of thehammer. This cycle repeats itself rapidly until either the tool breaksthrough and clear of the material being hammered or the operator, inorder to reposition the tool,

manipulates the necessary controls to lift the hammer so as to clear thetool.

The key feature of the above described automatic control of the hammeroperation is a positive disactivation of the hammer when the tool breaksclear or is lifted out of contact by the machine operator. In the firstplace, if the hammer operates with no load on the tool, the violentvibration of the hammer itself and the boom of the machine whichpositions it makes the hammer very diflicult to position as well asfrightening to the operator-the latter not being without cause. Whollyapart from the ability of the boom or other associated parts of amachine used to manipulate the hammer to withstand violent vibrations,the hammer itself is designed to withstand, with an ample factor ofsafety, the full impact of the ram 35 upon the tool 40 when the latteris subject to no resistance load, but not unlimited no-load driving ofthe ram upon the hammer. That is, the energy of a no-load impact of theram 35 upon the tool 40 can normally be safely taken up by the retainerhead 13 and the block 11 acted upon through the bolts 14 and intake head12, in sum, by the mass of the entire hammer. But if the hammer weredesigned to take up and dissipate the energy delivered by the ram 35over a prolonged period of noload conditions without rupture of someelement of the hammer, its mass with respect to the impact that could bedelivered under load would be so great as to make the hammer bothunwieldy to operate and uneconomical to make.

The successful positive disactivation of a hammer as above described,upon one no-load impact of the ram 35 upon a tool 40 depends uponseveral factors, two of which, preferably in combination, are notreadily apparent or calculatable but which can usually be determinedempirically. These factors-mot necessarily in the order of theirimportance-are: (a) the contour of the mating shoulders 47 and 48 withrespect to the mass of metal in the retainer head 13 and, particularly,the barrel 49; (b) the distance between the effective closing edges ofthe upper portion 41 of the tool shank and the port 30, when the tool isin the disactivated position shown in FIG. 4, with respect to theresiliencies under a full noload impact, of the ram 35, the hammer 10,and the tiebolts 14 plus, to a certain degree, the resilience of theintake head 12 and block 11. Discussing the latter factor first-indesigning any specific model of a hammer made according to the inventionto avoid continued operation under no-load conditions, it has been foundnecessary to visualize the hammer as though its elements were made ofrubber. That is, if the port is of insufficient diameter and/or locatedtoo close to the edge of upper tool shank portion 41, under no-loadimpact the ram will bounce back from its impact on the tool so as touncover the return port 28 while, at the same time, the tool 40 willbounce back from the impact of its band 43 upon the shoulder of thebarrel 49, closing the disactivating ports 30. Under such conditions,the hammer will thereby continue operating, until the air supply is cutoff, as though there were no provision for a no-load disactivation ofthe ram 35. Once the above cause of such ineffectiveness of thedisactivating port is discovered, the condition is usually cured byempirically lengthening the counter-bore 46 so as to drop the shankuntil trial and error demonstrates that the edge of the upper portion 41will not bounce into closing relation with the port 30. In regard to thecontour of the shoulders 47 and 48, because these shoulders provide astop which must resist the full impact of the ram 35 when the shoulder47 is in engagement with the shoulder 48, normal design principles woulddictate that there be a minimum filleting of the bottom of thecounter-bore 46 and the upper edge of the bore of the barrel 49 and thecorresponding surfaces of the band 43 and lower shank 42. The purpose ofminimizing such filleting would be to avoid the wedging action whichwould be expected to arise from such mating fillets and the consequentjamming and/or splitting of the barrel 49; also, the shoulders 47 and 48would then engage in planar contact perpendicular to the direction ofthe impact and thus, in normal theory, best positioned to resist suchimpact. In practice, however, it was discovered that such normal sounddesign of the shoulders 47 and 48 with a minimum of filleting apparentlypromoted the bounce of the tool and the hammer under full no-loadimpact; this in turn required not merely lengthening the depth of thecounter-bore 46, as described above, but also redesigning the cylinderblock 11 and upper tool shank 41 in order to achieve suflicient spacing(especially in some models designed for higher operating air presures)to allow the port 30 to effectively disactivate the hammer under noload. Instead, it was found that by enlarging the fillets of theshoulders 47 and 48 up to the maximum which would still provide aprojected area perpendicular to the direction of impact, the bounce isapparently decreased, thereby avoiding a need for excessive depth of thecounter-bore 46 and/or a lengthened design of the hammer. The decreasein bounce attributable to such full-filleted shoulders as shown in FIG.6 (i.e., fillets whose radii are approximately half the differencebetween the radius of the band 43 and the radius of the shank portion42) may be due to momentary wedging of the mating fillets; however, thecold-working of the shoulders 47 and 48 during break-in and useindicates that the momentary braking effect of the filleted shouldersmay be due to a momentary shrinking of the bore of the barrel 49 aroundthe lower shank portion 42.

I claim:

1, In a pneumatic impact hammer comprising a cylinder block providedwith a central bore, a ram reciprocal in said bore, an automatic valveclosing the inner end of said bore and which switches operating fluidfrom ports in the inner and outer portions of the bore so as toautomatically reciprocate said ram in said bore, a tool having a shankportion which closes the outer end of said bore and which is reciprocaltherein, said tool shank being reciprocal in said bore in response toand between the impact on the shank end of said tool imparted by saidreciprocal ram and pressure applied to the outer end of said tool, andmeans limiting the inner and outer reciprocal movement of said toolshank, said bore being provided with a return-disactivating port locatedin the portion of said bore traversed by said shank and communicatingsaid more to the atmosphere, said outer end of the ram in the lattersoutermost position along the bore being of substantially smallercross-section than the bore at said disactivating port and outward fromsaid disactivating port, whereby, when said tool shank is in itsoutermost position in said bore, any fluid pressure between the innerend of said shank and the outer end of said ram and tending to forcesaid ram toward the inner end of said bore is exhausted rapidly to theatmosphere through said disactivating port to disactivate areciprocating pressure on said ram until sufficient pressure is appliedto the outer end of said tool to force said tool shank inwardly andclose said disactivating port and whereby relief of such pressure on theouter end of said tool terminates reciprocation of said ram in saidbore, the length of the bore traversed by said tool shank being greaterthan the axial length of said disactivating port plus the axial distancesaid tool shank will be bounced inwardly by a resilient reaction to anoutward impact of said ram when there is substantially no opposingpressure on the outer end of the tool, said disactivating port beinglocated inwardly of the innermost distance to which said tool shank willbe bounced.

2. An impact hammer according to claim 1 and further comprising a toolretaining head on the outer end of said cylinder block, said toolretaining head having a bore in its outer end for passing the tool and acounterbore extending inward from said last-mentioned bore and alignedwith and opening into said cylinder block bore, said tool retaining headpresenting an inwardly-facing transverse 7 shoulder at the intersectionof its bore and counterbore, said tool having an enlarged annularportion slidably received in said counterbore and engageable with saidshoulder on the tool retaining head to limit the outward movement of thetool, the walls of said bore and counterbore in the tool retaining headmerging into said shoulder by oppositely curved arcuate fillets ofsubstantially equal radii, and the sum of the radii of said filletsbeing substantially equal to the difference between the radii of thecounterbore and the bore in the tool retaining head, said enlargedannular portion of the tool having curved portions at the radiallyoutward and radially inward extremities of its outer end which havecontours that substantially mate With the respective fillets.

References Cited UNITED STATES PATENTS 1,637,192 7/1927 Jimerson 173171,713,784 5/1929 Slater 173-17 3,398,801 8/1968 Kotone 173l6 10 ERNESTR. PURSER, Primary Examiner US. Cl. X.R. 173-17

